1. Field of the Invention
This invention relates generally to devices for suspending a person from the roof of a building, and relates more particularly to a wheel-mounted counterbalance support structure that can be rolled along the edge of the roof to facilitate the washing of the windows of the building.
2. Description of the Relevant Art
The task of washing or cleaning the windows of a building of more than a few stories in height involves the suspension of a person from the roof of the building. The person, a window washer, typically starts at the top of the building and gradually lowers himself downward, washing windows on the way. The window washer is suspended from above by a boatswains chair or other platform that is supported from above by one or more suspension ropes. The topside of the suspension ropes is secured in some fashion to the building or other structure.
Traditionally, the topside of the suspension ropes have been secured to davits that are fastened to the roof of the building and project over the edge of the roof. This securing arrangement is satisfactory in terms of safety, but can be expensive in implementation and inconvenient in use. In implementation, the providing of a sufficient number of sockets for mounting the davits can be expensive, especially if not planned into the construction of the building from the beginning. In use, the window washer and his suspension rig are confined to vertical movement and the suspension rig must be reattached to a different location on the roof after each vertical pass. The reattachment involves a good deal of lost production time while the window washer travels between the ground and roof levels and reattaches the suspension rig. The lost cleaning time caused by the reattachment of the suspension rig is especially a problem in low and medium height buildings where the repositioning of the suspension rig can involve a large percentage of the time required to wash the windows of the buildings due to the limited number of windows that can be washed during each vertical pass.
As an alternative to securing the suspension ropes and rig to davits, one company has offered a wheel-mounted support apparatus that can be moved around on the roof. This wheel-mounted support apparatus has a beam that at one end hangs over the edge of the building and provides an attachment point for the window washer's suspension rig. Inward from the attachment end of the beam is one wheeled support that rides on or close to the parapet. At the other end of the beam is a second wheeled support and means for attaching a counterweight. Both of the wheeled supports have two in-line wheels that are parallel to the edge of the roof. The counterweight is a block of concrete that is suspended from the inward end of the beam. The entire structure is designed for easy disassembly so that the apparatus can be moved to other job sites. Accordingly, the four wheels are mounted to legs, each of which is separately and removably attached to the beam.
In use, this wheel-mounted apparatus does overcome some of the disadvantages of using davits to secure the suspension rig, but introduces some disadvantages of its own. The wheels allow the apparatus to be pushed parallel to the edge of the roof by an operator stationed on the roof, but do not allow the apparatus to manuever around obstacles on the roof, such as heating and air conditioning structures, skylights, etc. The removability of the legs, unfortunately compromises the safety of the apparatus for the purpose of transportability between job sites. Also, the counterweight is not securely attached and if it should happen to fall off, the safety of the window washer will be in serious jeopardy.